This invention relates to an aqueous pharmaceutical composition comprising an active ingredient which is highly insoluble in water. In particular, it relates to a pharmaceutical composition in which the active ingredient is dispersed in liposomes.
A great deal of research is being carried out to find new liposomal preparations in the pharmaceutical field. However, many difficulties have emerged particularly in relation to active ingredients which are highly insoluble in water. In particular, those with a solubility in water xe2x89xa60.01% (w/v).
In fact, the technique currently used to produce liposomes comprising active ingredients of low water-solubility comprises:
a) solubilizing of the active ingredient and the preselected phospholipids in a suitable organic solvent, for example, chloroform;
b) evaporation of this solvent at reduced pressure to give an active ingredient/phospholipid film;
c) addition of a second organic solvent, for example, terbutylic alcohol;
d) freezing of the solution obtained at the temperature of liquid nitrogen;
e) lyophilisation of the frozen solution;
f) hydration of the lyophilised solution with a buffer solution to give a suspension of multilamellar liposomes (MLV); and
g) treatment of this suspension with ultrasound to give a suspension of smaller liposomes (SUV).
An example of this method is described by A. Sharma et al. xe2x80x9cPharmaceutical Researchxe2x80x9d, 2 (6), 889-896 (1994).
This technique, however, has the disadvantage of being very laborious and leads to the presence of traces of organic solvents in the liposomes. sphingolipids and mixture thereof. More preferably, they are made up of phospholipids. A typical example of the liposomal composition according to this invention comprises phosphatidylcholine, lysophosphatidylcholine, N-acyl-phosphatidylcholine, phosphatidyl ethanolamine, phosphat-idylserine, sphingomyelin, non-polar lipids, triglycerides, free fatty acids, DL-xcex1-tocopherol.
A preferred liposomal composition according to this invention comprises:
A particularly preferred liposomal composition according to this invention comprises:
Typically, the size of the liposomes according to this invention is less than 500 nm. Preferably, this is from 50-250 nm.
A second object of this invention is a method for the preparation of an aqueous pharmaceutical composition with an active ingredient which is highly insoluble in water, dispersed in liposomes, which is characterised by the fact that it comprises the following phases:
a) dispersion of this active ingredient in lipids at a temperature of between 20 and 30xc2x0 C.;
b) suspension of this dispersion in an aqueous phase;
c) resting of this suspension at ambient temperature for a period of between 0 and 48 hours;
d) heating to 30-75xc2x0 C. for 10-40 minutes;
e) freezing at xe2x88x92150/xe2x88x92200xc2x0 C.;
f) repetition of phases d) and e) at least twice and not more than 8 times;
g) filtration through a filtering membrane with pores of diameter 500-1000 nm;
h) extrusion through a membrane with pores of diameter 50-400 nm; and at the same time
i) removal of any active ingredient which is not trapped.
The duration of phase c) depends on the quantity of active ingredient highly insoluble in water to be trapped in the liposomes. The person skilled in the art does not therefore encounter any difficulties since a few simple routine experiments will determine the correct time for each type of active ingredient and liposomal composition.
The aqueous phase shall preferably be made up of an aqueous solution of sodium chloride at 0.05% -0.9% (w/v).
Typically, the quantity of lipid used is between 0.01-0.4 parts by weight for each part by weight of aqueous solution. In turn, the quantity of active ingredient is typically between 0.01 and 0.3 parts by weight for each part by weight of lipid.
Typically, the disperser is a homogeniser of the Ultraturrax(trademark) type.
Typically, the extrusion is carried out using compressed air or an inert gas, chosen from the group comprising nitrogen, helium and argon, as the extrusion gas. The preferred inert gas is helium. In the extrusion phase, the pressure shall preferably be between 500 and 5500 kPa and the temperature shall preferably be between 20 and 75xc2x0 C., and even more preferably between 40 and 65xc2x0 C. Typical examples of suitable extruders are those of the Lipex Biomembranes Thermobarrel type or of the Emulsiflex CC Avestin type with filters with polycarbonate Costarm membranes with pores of between 50 and 600 nm.
Typically phase h) is repeated at least twice and not more than 8 times. Preferably 6 times.